Jacket sleeves typically consist of two parts--a top sleeve and an under sleeve. After the top sleeve and the under sleeve are assembled and joined, the sleeve forms a tube. The end of the sleeve is designed such that it is not perpendicular to the center line of the tube. This sleeve is then mated to an armhole on a jacket. The armhole itself is created by the assembly of three parts--the back, front and side body. The resulting armhole opening is slightly more eggshaped than round. Normally, alignment notches are located on the periphery of the armhole opening and the end of the sleeve. These alignment notches are utilized during the sleeve setting operation to assure the proper orientation of the sleeve with respect to the armhole and also to assist the operator in distributing the excessive "fullness" in the sleeve as it is set into the armhole. Suitable fullness is required to provide a visually satisfactory style, as well as desirable fit to allow arm movement. Fullness is determined by the relative length of material around the periphery of the sleeve opening that is matched with the length of material around the armhole. For example, the distance between two notches on the armhole can be spaced at approximately two inches whereas the distance between two mating notches on the sleeve may be 2.5 inches. This results in fullness due to a longer length of sleeve material being matched to a corresponding length of armhole material.
Because of styling and fit considerations, the fullness distribution of the sleeve with respect to the armhole is not uniform along the entire periphery of the armhole. For example, more sleeve fullness is required at the top of the shoulder to allow the sleeve to "roll over" and hang properly. Likewise, no sleeve fullness is required across the bottom of the armhole for comfort reasons. In addition, there must be no localized discontinuities in the fullness distribution since this will result in "dimples" or "pinch marks" on the periphery of the sleeve. Therefore, it is very important that the operator control the fullness distribution on a localized as well as an overall basis, such that the sleeve hangs at the proper angle, the roll in the sleeve is aesthetically pleasing and there are no localized discontinuities which distract from the appearance of the garment.
Sewing machine manufacturers have developed machines which have a variable top feed mechanism in order to handle sewing operations which require fullness of one material ply relative to the other ply. These machines have independent feeding mechanisms to feed the bottom and top plies of material such that the distance the feeding mechanism advances for each stitch can be adjusted independently for the bottom and top feed mechanisms. Thus, if fullness is required in the top ply of the material, the top feed mechanism is adjusted to advance a greater distance than the bottom feed mechanism during the stitch formation. If no fullness is required, the top and bottom feed mechanisms are set to advance the same distance during the stitch formation. Finally, the top feed mechanism can be adjusted to advance less than the bottom feed during stitch formation if it is desirable to sew fullness in the bottom ply material.
When a sewing machine operator is setting a jacket sleeve, the top feed mechanism must be varied in order to produce the fullness distribution desired. In the past, different techniques have been employed to vary the top feed mechanism as the sleeve is being set. One technique is to utilize a foot treadle which is mechanically linked to the top feed mechanism. As the operator sews the part, she depresses the foot treadle to advance or retard the top feed mechanism in order to provide the proper amount of fullness. Since the sleeve part is sewn as the top ply material, and it is desirable to sew in excess fullness in the sleeve relative to the armhole, the top feed mechanism is set to give equal or more than equal feed on the top ply. Additional enhancements have been made to variable top feed machines by adding optical scales and/or gauges which graphically illustrate to the operator the amount of top ply that is currently being sewn relative to the bottom ply. For example, a Durkopp 541 sewing machine has a fish scale type mechanism which advances a pointer from 0 to 9, as the top feed mechanism is advanced from no top feed to maximum top feed by depression of the foot treadle. In a similar manner, the Pfaff 337 sewing machine utilizes a set of five indicator lights which are arranged in a vertical orientation. As the operator depresses the foot treadle to increase the top feed from no top feed to maximum top feed, the lights are progressively lit.
In the more advanced mechanisms that have been developed, a cam is utilized to control the top feed mechanism as the sleeve is set. This cam mechanism is mechanically linked to the top feed mechanism by way of a cam follower which rides on the cam which is rotated one complete revolution during the sewing operation. An example of this type of mechanism is the Tecmics model LS3-302 sewing machine with optional accessory model 1KD.
Recently, microprocessors have been used to facilitate the storage of a series of top feed values which can be easily requested by the operator as the operation is being performed. For example, the Adler model 550-16-1 sewing machine has the capability to store top feed values with each value in the range of 0 to 9 representing 0% to 100% top feed. As the sleeve is being set, the operator activates a switch which causes a stepper motor to adjust the top feed mechanism to the next stored value.
Although the above described systems deskill the operation and improve quality to a varying degree, they have not solved the overall problem of accurately controlling the top feed mechanism when sleeves are set. In view of these deficiencies, there exists a need for a system which automatically controls the top feed to compensate for differences in size, material type, material bias and sewing direction during the sleeve set operation.